Island



March 10. 1925. v 1,529,209

J. w. PARKER PROTRACTOR Filed Dec. 15, 1923 Amy/A 4 Patented Mar. 10, 1925.

UNITED- STATES 1,529,209 PATENT OFFICE.

JOHN w. PARKER, OFBAR-RINGTON, anionic ISLAND, nssren oa tronaowlv casualti s MANUFACTURING Comrenv; or" PROVIDENCE, RHODE ISLAND.

PROTR-ACTOR.

Application filed December 15, 1923. Serial No. 680,939.

To all whom it may concern: I

Be it known that I, JOHN W. PARKER, a citizen of the United States, residing at Barrington, in the county of Bristol and State of Rhode Island, have invented new and useful Improvements in Protractors, of

which the following is a specification.

This invention relates to certain new and useful improvements in protractors and pertains more particularly to means for securing a rule to a protractor head.

The primary object of the invention is to provide improved means for enabling the rule to be secured to the head of a protractor whereby the rule may be easily and quickly removed from the head and the rule reversed to thereby enable reading of the four series of graduations disposed along the longitudinal side edges of the respective faces of the rule.

A further object of the invention is to provide simplified and economical means for reversibly attaching the rule to the head.

Further and other objects will be later set forth and manifested in the course of the following description.

In the drawings Figure 1, is a side elevation of the invention partly in section, showing same applied to one form of protractor head, the rule being shown in fragment;

Figure 2 is a section on line 2-2 of Fig ure 1.

Figure 3, is a detail view of the attaching pin, and

Figure 4:, is a section on line 1--4 of Figure 3.

The drawings illustrate the invention applied to one form of a protractor head indicated at H, it being understood however that the invention is equally applicable to centre heads, square heads and heads of varying forms. The rule indicated at R is of standard form and is provided with two series of graduations on each of its two or opposed faces, and is received in a slot provided therefor in the head.

In proceeding in accordance with the present invention, the rule is provided with a longitudinal groove 1 extending centrally of its width on one side face thereof. A hole 2 is drilled through the head and has a counterbored or enlarged lower end 3.

A clamping screw or pin is employed having a body 4, the upper end of which has a lowed by tightening of the nut.

9, which latter is preferably of substantially 5 semi-circular cross-section and projects outwardly from the flat face 8 as shown in Fig ure 2, the rib conformably engaging in the roove 1 of the rule. I

The ends of the rib extend outwardly beyond the side edges of the face 8 so as to increase the effective holding action of the rib against the walls defining the groove 1 in the rule, which is accomplished by displacing the shank of the pin at opposite edges thereof as indicated at 12. The rib 'is of greater length than the diameter of the screw and of the hole and thereby prevents inward movement of the screw into the hole.

A knurled thumb nut 10 is engaged over the threaded end 5 of the pin and encloses a coil spring 11, the latter encircling the end 5 of the pin and exerting tension on the nut to hold the latter against accidental rotation.

In order to remove the rule from the head to reverse the rule, it is merely necessary to loosen the nut 10, so as to permit the pin and thereby rib 9 to extend in the enlarged end of the hole 2 to allow the rib to be disengaged from the groove 1 of the rule, whereupon the rule is removed, the pin is given a half turn, and the rule reversed and again engaged with the pin rib, fol- From the above it will be noted that the two keyways and fastener pin commonly used with the main pin or clamping screw are dispensed with, it being merely necessary to slightly slide and then give the pin a half-turn in removing and reversing the rule, without complete removal of the pin, as heretofore practiced in the art.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is In combination with the head of a protractor having a rule-receiving slot and having a hole, the latter counterbored at the outer portion of the head, a rule in said slot formed with a longitudinal groove on ainto the hole, and means on the screw to 1 face thereof, a Clamping "sc'r'ew in the hole clamp the rib 'agtinst thei'nle. having atransverse integral rib on its In testimony whereof I have signed my outer end, said rib being received in the ngune to this speoifioation in the presence of i c'o'untefboied oiite'r end of the hole 5nd b e-r two subscribing witnses. H 7

ing of greatei' length then the dienietei of JOHN W. PARKER. the screw and of the hole so as to p 'event Vitnesses: movement of the rib into the hole and there- S. N. BARRY,

by prevent inward movement of the screw J. A. MILLER. 

